1. Field of the Invention
The present invention relates to a technique for ensuring data security in a system that realizes provision of on-demand storage areas.
2. Description of Related Art
Through the widespread use of the Internet these days, storage services for providing storage areas to users via a network are provided. Using this service, a user does not have to purchase, maintain, or manage a storage system by himself. If it becomes no longer necessary to use the storage system, all the user has to do is to terminate a contract with a service provider. Accordingly, the user can utilize the storage system easily. Recently, there has also been a storage on-demand service that allows a user to easily use a storage system in any required capacity whenever necessary and charges the user for as much storage system as they used.
For example, a storage operation method is suggested by which, if it is found that the remaining storage area capacity of a user's storage system has become less than a specified value, a storage area in a remote storage system connected via a specified communication means to the user's storage system is made available as a storage area for the user's storage system (see JP-A-2003-30013).
Furthermore, a storage service method, a storage service program, and a storage apparatus that can easily set storage use capacity as desired by the user and charge a usage fee to the user for the actually used storage capacity have been suggested (see JP-A-2004-21796).
If a service provider provides a storage area to a user via a network, and if the user terminates a storage use contract or reduces the storage capacity provided by the service provider, the service provider will provide that storage area, which is no longer used by the user, to another user as a matter of course. In this case, information stored in the storage area by the former user will be deleted without fail, so even if that storage area is reassigned to another user, the former user's data will never be read or viewed by the new user.